Electrochemical properties of NiS as a cathode material for rechargeable lithium batteries prepared by mechanical alloying

Nickel sulfide (NiS) as a cathode material for a lithium rechargeable battery is charged and discharged at room temperature (30 degreesC). In order to synthesize a homogeneous NiS phase, mechanical alloying (MA) was adopted. The homogeneous NiS phase is easily formed after ball milling for 12 h under Ar atmosphere. The ball-milled NiS particles are relatively larger than those of the starting materials and have a nanocrystalline structure. The initial discharge capacity of the NiS positive electrode is 580 mAh/g-NiS, at 1.4 V versus Li/Li+. The NiS powders synthesized by MA show proper cycling properties, by retaining 65% of the initial discharge capacity even after 100 cycles at 30 degreesC. Also, NiS has a good rate capability. It has 87% of its theoretical capacity at a current rate of 2 C, comparable with that of 1/6 C. (C) 2002 Elsevier Science B.V. All rights reserved.